Explosive projectile



3 Sheets-Sheet '1 INVENTORS AITOR Nev:

S p 5 NILS-ERIK G. KULLER ETAL EXPLOSIVE PROJECTILE Filed Jan. 11, 1954 NILS-ERIK GUSTAF KULLER NILS DAVID SVEN GOSTA GERTZELL FIG P 1958 NlLS-ERIK G. KULLER ETAL 2,849,957

EXPLOSIVE PROJECTILE Filed Jan. 11, 1954 5 Sheets-Sheet 2 INVENfIORS NlLS-ERIK GUSTAF KULLER NILS DAVIDBVEN GOSTA GERTZELL I QM ATTORNEY.

NlLS-ERIK G. KULLER ETAL' 2,849,957

Sept. 2, 1958 EXPLOSIVE PROJECTILE 5 Sheets-Sheet 3 Filed Jan. 11, 1954 v FIG. 6

L Y L RE EZ MLT M TLR E NNUE N K 04 m T F T um A ano (G N ME RV S DY WM D S l N 4 3 5 5 3 G M F. L?

2,849,957 Patented Sept. 2, 1958 ice EXPLOSIVE PROJECTILE Nils-Erik Gustaf Kiiller and Nils David Sven Gosta Gertzell, Karlskoga, Sweden, assignors to Aktieholaget Bofors, Bofors, Sweden, a Swedish corporation Application January 11, 1954, Serial No. 403,356

Claims priority, application Sweden January 27, 1953 8 Claims. (Cl. 102'70.2)

The present invention relates to explosive projectiles, more specifically to the firing mechanism for setting oif the explosive charge of the projectile, particularly of a projectile with hollow charge effect.

There are known projectiles with hollow charge effect in which a detonator is disposed in the rear part and a percussion fuse in the nose of the projectile. This fuse, on impact, spurts a jet of flame through a hollow cone in the front part of the projectile and a continuing tube in the rear part against the detonator which in turn sets off the explosive charge. Practical experience has shown that the aforesaid design of explosive projectiles is rather unsatisfactory from a manufacturing view point. It has been found to be 'difiicult to mount the cone and the tube extending therefrom within the projectile and to fill the projectile with its explosive charge.

Accordingly, one of the objects of the present invention is to provide a novel and improved explosive projectile, particularly a projectile of the hollow charge type, which can be readily and conveniently assembled and filled with the explosive charge.

Another object of the invention is to provide a novel and improved design of the firing mechanism which eliminates the necessity of a tube leading from the hollow cone in the front part to the detonator in the rear part. Such a design not only simplifies the manufacture and assembly of the projectile but also affords the advantage that the chamber for the explosive charge is free of bstructions thereby facilitating the filling of the projectile.

Still another object of the invention is to provide a novel and improved firing mechanism in which the jet of flame heretofore used to activate the firing mechanism 7 is replaced by electric means rendered operative by impact for the purpose aforesaid.

A further object of the invention is to provide a novel and improved firing mechanism in which the potential required to set off the detonator is generated by the impact experienced by the projectile when it strikes an obstacle.

Other and further objects, features and advantages of the invention will be pointed out hereinafter and set forth in the appended claims forming part of the application.

In the accompanying drawing several now preferred embodiments of the invention are shown by way of illustration and not by way of limitation.

In the drawing:

Fig. 1 is a longitudinal sectional view of a projectile equipped with a firing mechanism according to the invention.

Fig. 2 is a sectional view similar to Fig. 1 and showing a modification of the firing mechanism.

Fig. 3 is a fragmentary sectional view of the conical front part of a projectile equipped with another modification of the firing mechanism.

Fig. 4 is a longitudinal sectional view of still another modification of the firing mechanism.

Fig. 5 is .a sectional view similar to Fig. 4 showing yet another modification of the firing mechanism, and

Fig. 6 is a fragmentary sectional view of the joint between the front part and the rear part of the projectile.

Referring first to Fig. 1 in detail, the projectile according to this figure comprise a generally cylindrical rear part 1 and a generally conical front part 3. Both parts are made of metal. A conical metal member 2 facing with its apex the base of the casing formed by parts 1 and 3 is mounted within the casing and provided for this purpose with an outwardly threaded cylindrical flange which engages internally threaded edge portions of parts 1 and 3 thereby joining the said parts.

Part 3 is truncated and recessed to provide space for a nose portion 4 which completes the cone-shape of part 3 and is threaded in the correspondingly threaded recess of front part 3. Nose 4 has an axial bore in which is fitted a cup shaped metal member 5 resting with its bottom against the base of the axial bore in nose 4. Cup 5 is lined with a liner 6 made of insulation material. The lined cup serves to receive therein an electrically conductive disc 7 abutting against the metal of the bottom of cup 5, a disc 8 made of a material capable of generating an electric voltage in response to a deformation induced by mechanical stresses and strains, .an electrically conductive disc 9, a disc 10 preferably made of insulation material and a flanged locking member 11 threaded in cup 5 thereby pressing the stack formed by the aforesaid discs 7 to 10 tightly together and against the bottom of cup 5.

Disc 8 is preferably a slab of a crystalline substance, more particularly of one of the twenty crystal classes that are now known to exhibit the piezoelectric phenomenon of generating a voltage in response to deformations induced in the substance by external forces. Crystalline substances of this type are for instance quartz, Rochelle salt, or lithium sulphate. Recently, piezoelectric ceramics have also been developed. Ceramic materials of this type are polycrystalline in nature, basically made up of barium titanate and subjected to a special polarizing treatment. Generally speaking, all materials that are now known or may become known in the future which exhibit the piezoelectric phenomenon are suitable for the purpose. Discs 9 and 10 and member 11 are pierced for the insertion of a metal wire 12 in electric contact with one side of crystalline disc 8. A sleeve or bushing 13 may be provided to guide and protect the wire.

Casing part 3 is lined with an insulation layer 14 and an electrically conductive layer 15 to which the outer end of wire 12 is connected for instance, by soldering. Similarly, cone 2 is lined with an electrically conductive layer 17 insulated from the wall of the metal cone 2 by an insulation layer 18. The conductive layers 15 and 17 are connected by a contact spring 16 secured on one end to conductive layer 15 and engaging with its free end layer 17.

Casing part 1 is also lined with a layer 22 electrically insulated from the wall of the casing part by an insulation layer 23. An insulation bushing 19 is fitted in and through the wall of cone 2. A wire 20 is extended through this bushing. One end of the wire is in electric contact with conductive layer 17 and the other end ends in or supports a contact spring 21 pressing with its free end against the conductive layer 22 in casing part 1.

The bottom of casing part 1 has a comparatively wide opening in which a plug 24 is threaded and a second rather narrow bore 29 which may be closed by a plug 30.

Plug 24 is formed with a chamber 25 which is accessible through an opening closed by a cover 24a secured in the opening by screw threads or other suitable means. Chamber 25 is filled with a combustible material suitable for use in a detonating device. Various materials of this 'and 18.

riveting or any other suitable means.

serves to establish electric contact between cup and crystalline disc 8 is connected with one terminal of primer 26 through wire 12, conductive layer 15, contact spring 16, conductive layer 17, contact spring 21, conduc tive layer 22 and contact spring 27. The other side of crystalline disc 8 is connected with the second terminal of the primer through metal disc 7, cup 5, casing part 3, :casing part 1 and plug 24.

The insulating layers 14, 18 and 23 may consist of a suitable liner material or may be produced directly on the respective walls by spraying or a similar operation. -The conductive layers 15, 17 and 22 may consist of foil :or be directly produced on the respective insulation layers -by electrodeposition, spraying or painting with a conductive paint or ink, etc.

The hollow space circumscribed by cone 2 and the walls of casing part 1 is filled with an explosive charge '31. Forpurpose of filling the projectile, plugs 24 and 30 are removed. Explosive material is then fed into the casing through the large opening up to a level such that when the plug 24 is replaced the contact spring 27 will make firm contact with conductive layer 22. Plug 24 is ,then tightened and further explosive charge is filled into the casing through bore 29 until the available space in the casing-is completely filled.

The fact that cone 2 does not require an opening in its apex for inserting therein the aforementioned tube for guiding a jet of flame considerably facilitates the filling operation.

The operation of a projectile as hereinbefore described, is as follows:

Let it be assumed that the projectile has been fired and finally strikes the target or another obstacle. As a result, nose 4 will exeperience a strong impact which is transmitted to disc 8. The stress and strain and the deformation experienced by disc 8 causes the same to develop a voltage by reason of the piezoelectric phenomenon. The generated voltage heats primer 26 thereby igniting the detonating material which inturn will set oft the explosive charge 31.

The projectile according to Fig. 2 is similar to the projectile according to Fig. 1, with the exception that the conductive layers 14 and 15 are replaced by bands 14' and 15' and similarly the layers 17 and 18 by bands 17' The contact spring electrically connecting the conductive bands 15' and 17' is correspondingly extended and designated by 16'.

Fig. 3 shows a projectile the actuating or control means of which are similar to the ones previously described and hence designated by the same reference numerals. However, the metal cone 3 of Figs. 1 and 2 is replaced by a cone 3 made of insulation material, such as a plastic known under the name Bakelite. The electric conductors leading from both sides of the piezoelectric disc 8 are shown as a plurality of parallel wires 32 and a wire netting 33. Both the wires and the netting are embedded in the insulation material. It will be evident that conductor 33 may be in from of parallel wires and conductor 32 in form of a netting or both conductors may be made of parallel wires or netting. Wire netting 33 is in electric contact with contact spring 16 with which it may be connected by exposing part of the wire netting, Conductor 32 metal casing part 1. For this purpose, the wires of conductor 32 are shown to protrude from the outer edge of casingpart 3'. The wire ends may also be cut ofl? flush with the rim of part 3 in which case the cross-sectional area of the wires is used to make contact. To further improve the contact connection, contact plates or a contact ring may be fitted to the edge of part 3'.

It will be apparent that conductor 33 may also be used to make contact with casing part 1 in which case conductor 32 is connected with contact spring 16.

The projectile according to Fig. 4 is distinguished from the previously described exemplifications of the invention according to Figs. 1 and 2 in that the conductive and insulation layers or bands in casing part 3, cone 2 and casing part 1 and the contact springs coacting therewith are omitted and replaced by a cable 12' connecting the respective side of disc 8 with primer 26. For this purpose cable 12' is extended through an insulation bushing 34 in the bottom of easing part 1 and a similar insulation bushing 35 is fitted in the larger plug designated by 24'. The design of the chamber formed in the plug is also slightly changed in that bushing 28 is omitted and the cover plate is made wider and designated by 24a.

The projectile according to Fig. 5 employs as voltage generating means a device 39 which may be visualized as a dry cell or a small storage battery. It may also be visualized as a capacitor charged from a suitable source of current. The voltage generating device 39 is situated in the chamber 25 of plug 24" closed by a cover member 24"a. One of its terminals is directly connected with the plug. The other terminal is connected by cable 12' with control means situated in nose 4. These control means are shown as two contact studs 37 and 38 held spaced apart by a spring 36 which is electrically insulated from metal discs 7 and 9. As is apparent, disc 7 is in electric contact with plug 24 through cup 5 and the casing walls and disc 9 is in contact with the respective terminal of primer 26 through cable 12'.

When the projectile according to Fig. 5 hits a target, the impact experienced by its nose 4 will cause engagement between the contact studs 37 and 38 thereby closing an energizing circuit for the device 39 which will activate primer 26.

Fig. 6 shows an arrangement in which the cone now designated by 2' is integral with casing 1, the outside rim of the cone is threaded so that casing part 3 of the casing can be joined to casing part 1' and the cone by a thread connection. The cone and the casing can also be joined by welding operation.

The arrangement according to Fig. 6 can be used in connection with any of the previously described embodiments of the invention.

Although the invention has been described in reference to projectiles with hollow charge efiect as it is particularly advantageous in connection with projectiles of this type, it should be understood that the invention is also applicable to projectiles without an internal cone and filled partly or completely with an explosive charge.

While the invention has been described in detail with respect to certain now preferred examples and embodiments of the invention it will be understood by those skilled in the art after understanding the invention, that various changes and modifications may be made without departing from the spirit and scope of the invention, and it is intended, therefore, to cover all such changes and modifications in theappended claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. An explosive projectile of the hollow charge type, comprising a casing composed of a lower casing part closed at its lower end by a bottom wall having an open ing therethrough and open at its upper end, an inner conical casing part fitted facing downwardly in the open end of the lower casing part, said lower casing part and said conical casing part defining a chamber for an explosive charge, an outer generally conical upper casing part hava conductive layer supported-on'an inner Wall of each of said three casing parts electrically insulated therefrom, said three layers being electrically separated from each other, an electrically operable igniting means fitted in said bottom opening, for detonating the charge in said chamber, an impact responsive source of voltage for energizing said igniting means fitted in said apex opening, and electrical conductor means within the casing interconnecting said three conductive layers with each other and said voltage source and said ignition means in a continuous circuit connection.

2. An explosive projectile of the hollow charge type,

' comprising a metal casing composed of an outer lower casing part closed at its lower end by a bottom wall having an opening therethrough and open at its upper end, an inner conical casing part fitted facing downwardly in the open end of the lower casing part, said lower casing part and said conical casing part defining a chamber for an explosive charge, an outer generally conical upper casing part having an opening in its apex and being fitted at its base upon said lower casing part, a layer of insulation material covering at least partly the inner wall surface of each of said three casing parts, a conductive layer adhered to the outside of each of said layers of insulation material, said conductive layers being electrically separated from each other, an electrically operable igniting means fitted in said bottom opening, for igniting the charge in said chamber, an impact responsive source of voltage for energizing said igniting means fitted in said apex opening, and electrical conductor means within the casing interconnecting said conductive layers with each other and the voltage source and the igniting means in a continuous circuit connection.

3. An explosive projectile according to claim 2, wherein said conductor means comprise a first conductor connecting said source of voltage with the conductive layer in the upper casing part, a second conductor connecting the conductive layer in the upper casing part with the conductive layer in the inner conical casing part, a third conductor connecting the conductive layer in the inner conical casing part with the conductive layer in the lower casing part, and a fourth conductor connecting the conductive layer in the lower casing part with said igniting means.

4. An explosive projectile according to claim 3, wherein said second, said third and said fourth conductor engage at one end a conductive layer with a spring pressure contact, the other end of the conductors being secured to a respective other conductive layer.

5. An explosive projectile according to claim 3, wherein said third conductor extends through the metal wall of said inner conical casing part, electrically insulated therefrom.

6. An explosive projectile according to claim 2, wherein said conductive layers are formed of metal foil adhered to said insulation layers.

7. An explosive projectile according to claim 2, Wherein said conductive layers are in the form of metal depositions on said insulation layers.

8. An explosive projectile according to claim 1, wherein said upper casing part is made of insulation material and wherein the conductive layer thereof is in the form of a wire netting embedded in the material of the casing part.

References Cited in the file of this patent UNITED STATES PATENTS 2,485,887 Jordan Oct. 25, 1949 2,672,094 Roberts Mar. 16, 1954 2,728,296 Meister Dec. 27, 1955 FOREIGN PATENTS 277,052 Switzerland Nov. 1, 1951 1,057,997 France Nov. 4, 1953 

